1. Field of the Invention
The invention relates generally to electro-optic waveguides and, more specifically, to fiber optic waveguides utilizing a core or surface layer of non-linear optical (NLO) polymer which has been poled to induce a permanent molecular orientation.
2. Description of the Prior Art
Planar electro-optical (E-O) devices in which an applied voltage induces a change in refractive index substantially proportional to the applied voltage are well known in the art. See, for example, U.S. Pat. No. 4,767,169, "Thin Film Waveguide Electro-Optic Modulator". Such devices can be constructed to form waveguides, switches, or modulators, for example, and may utilize interference effects, directional coupling, or rotation of the plane of optical polarization. Extensive background studies may be found in "Nonlinear Optical Properties of Organic and Polymeric Materials", D. J.Williams, Ed., ACS Symposium Series 233, Washington, D.C. (1983), which is hereby incorporated by reference.
While electro-optical devices utilizing bulk-grown inorganic crystals as the propagating medium are well known and widely utilized, they are difficult to grow and process and are limited in bandwidth response. Planar E-O waveguides have also been constructed using certain organic and polymeric materials which exhibit substantial non-linear responses when poled, and provide high damage-free thresholds against the operative electric fields and applied laser beams. However, after formation, the delicate polymer films are subject to mishandling and mechanical damage. In addition, the high-intensity electric fields necessary to polarize the medium (e.g., field strengths in excess of 100,000 V/cm) can induce structural damage to the polymer.
The present invention provides for encapsulating the polymer in an optically transparent hollow fiber to provide physical protection during poling and subsequent handling without impairing the desired optical properties.